Left columns: thumbnail images of the 13 UCDs that were found to have a half-light radius above 23 pc, which we adopted as limit for a reliable measurement. Right-hand column: next to each UCD residuals after subtracting the best-fit single Sérsic model from the observed image. Each UCD is labeled with its identifier number among the 97 UCDs in both FORS fields. Their properties are listed in detail in Table 1.